dashboard: remove fake ARM5 builders
dashboard: remove fake ARM5 builders

The spacemonkey actually-ARM5 builders have been working and are better.

The arm5 builders being deleted here were Scaleway C1 servers (which
have better-than-ARM5 hardware) but running with GOARM=5-compiled
binaries. That test a bit, but not enough.

Fixes golang/go#19662
Fixes golang/go#19848 (looks like this is only missing owner annotation)

Change-Id: I1d3b21b0139d4d4ccf2c0baebd4f2f01b4024861
Reviewed-on: https://go-review.googlesource.com/41618
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build